Staff members with the Oahu Army Natural Resources Program, Directorate of Public Works-Environmental, U.S. Army Garrison-Hawaii, discovered a Chromolaena infestation during routine road surveys in the Kahuku Training Area on the North Shore.

OANRP staff submitted the specimen to the Bishop Museum’s Oahu Early Detection program, and museum botanists verified that the specimen was Chromolaena " considered one of the 100 worst weeds in the world.

-Origins

Chromolaena thrives everywhere, except in deep shade, and it’s toxic to humans, livestock and even other plants. It’s native to Central America, but has skipped about the world and across the Pacific, infesting every island it has come into contact with.

Each shrubby plant grows up to 12 feet tall and can produce 800,000 seeds in a year. The small, narrow seeds, topped with a tuft of fibers, are easily dispersed via the wind. The small seeds can burrow into clothing, gear and fur, and they can move quickly along infected trails and roads. Cut branches can also root and grow into new, healthy plants.

A few plausible scenarios exist as to how Chromolaena got here. Perhaps a contaminated seed was planted in the agricultural area below KTA. Or a seed rode in on a dirt bike, since part of KTA is used for public motocross track on weekends. The most likely cause for the weed infestation, though, is military training.

Occasionally, units from Guam train in Hawaii, so tiny Chromolaena seeds, hidden in packs or boots, could have hitched a ride with one of these units.

-Significance

The discovery of Chromolaena in KTA highlights the importance of maintaining strict sanitation on training ranges.

Soldiers and contractors are asked to take advantage of wash racks at training ranges to clean wheel wells and undercarriages on tactical and other vehicles.

Hikers and range workers are asked to inspect their boots, clothes, packs and other field gear before entering natural areas. They are also asked to clean mud and debris off their gear at the end of every field day, and to wash and vacuum their vehicles at least once a week.

These efforts and those of the OANRP staff and its partners will help prevent species like Chromolaena from invading Hawaii.

OANRP staff, with help from the Oahu Invasive Species Committee, Bishop Museum and the Hawaii Department of Agriculture, is developing a detailed map of the Chromolaena infestation boundries in KTA. This map will be the first step in creating a comprehensive plan for addressing this highly-invasive species.